30-second video: one job, two 15 s jobs or three 10 s jobs?

Splitting a 30-second video into two 15-second or three 10-second jobs costs the same as, or a few cents more than, one 30-second job, because Sume bills list x 1.25 linearly in seconds and rounds up once per job. The savings from splitting are not in price; they are in which models you can use, and in how many retakes you pay for.

The same 30 seconds, three ways

Rows are 16:9 and use the tier shown. Kling 3 renders 1080p only and stops at 15 seconds, so one 30-second job is not possible on it.

Why split anyway

A retake of a 10-second shot costs a third of a retake of the whole 30 seconds. If one shot in three fails review, three 10-second jobs plus one retake costs $23.12 on Seedance 2.5 at 720p, against $34.68 for rerunning the single job.

Splitting also lets you mix models: a Wan 3.0 establishing shot with a Seedance 2.5 close-up. The joins then need a timeline step, which is billed separately.

When one job is better

A single request keeps one continuous motion and one set of audio. For 30-second dialogue or a single camera move there is no seam to hide, and the model is Seedance 2.5 or Wan 3.0 either way.